Liquid crystal display devices, which have small thicknesses and low power consumptions, have been used widely in various fields. Particularly, active matrix-type liquid crystal display devices including a thin film transistor (TFT) for each pixel, which have high specifications with high contrast ratios and desirable response characteristics, have been used in TVs, monitors, laptop computers, and the like, and have recently extended their market size.
An active matrix-type liquid crystal display device includes an active matrix substrate having a plurality of TFTs formed thereon, and a color filter substrate provided so as to oppose the active matrix substrate, wherein the orientation of the liquid crystal layer sandwiched therebetween is controlled to produce a display.
In addition to the TFTs, the active matrix substrate includes a large number of gate bus lines for supplying scanning signals to the TFTs, and a large number of source bus lines for supplying display signals to the TFTs. An active matrix substrate is produced by repeating a step of depositing a semiconductor film, an insulating layer and a conductive film on an insulative substrate, and a step of patterning these films. Therefore, a wire break may occur along a bus line (the gate bus line or the source bus line described above). Signals are no longer properly supplied to TFTs of pixels located downstream of the wire break location, and those pixels can no longer produce an intended display.
Thus, a wire break along a bus line can lead to a display defect. In view of this, techniques have been proposed in the art to repair a display defect arising from a wire break along a bus line by using repair lines provided in the bezel region (non-display region).
For example, Patent Document No. 1 discloses a display device including a first, second and third repair line provided in the non-display region. In this display device, the plurality of source bus lines (drain bus lines) are grouped into m groups. For each group of source bus lines, there are n first repair lines, and each of the n first repair lines crosses all the source bus lines of the corresponding group with an insulating layer interposed therebetween. On the opposite side from the first repair lines with respect to the display region, there are n second repair lines for each group of source bus lines. Each of the n second repair lines also crosses all the source bus lines of the corresponding group with an insulating layer interposed therebetween. There are 2×n third repair lines provided so as to cross all (i.e., m×n) second repair lines with an insulating layer interposed therebetween. One end of the first repair line and the other end thereof are electrically connected to the corresponding third repair line. The opposite ends of the second repair line cross the third repair line.
If a wire break occurs along a source bus line in the display device of Patent Document No. 1, the intersection between the broken source bus line and the first repair line is irradiated with laser light to make an electrical connection therebetween, and the intersection between the broken source bus line and the second repair line is irradiated with laser light to make an electrical connection therebetween. Moreover, the intersection between the second repair line, connected to the broken source bus line, and the third repair line is also irradiated with laser light to make an electrical connection therebetween. Thus, a portion of the broken source bus line that is upstream of the wire break location and a portion thereof that is downstream of the wire break location are electrically connected to each other via the first, second and third repair lines. This allows for a display signal to be supplied across the entirety of the broken source bus line.